// Remove the inuse_ prefix to support legacy pprof options
	// "inuse_space" and "inuse_objects" for profiles containing types
	// "space" and "objects".
	noInuse := strings.TrimPrefix(sampleIndex, "inuse_")
	for i, t := range p.SampleType {
		if t.Type == sampleIndex || t.Type == noInuse {
			return i, nil
		}
	}

	return 0, fmt.Errorf("sample_index %q must be one of: %v", sampleIndex, sampleTypes(p))
}

// in math/big.Int.ModInverse) although math/big itself isn't strictly
// constant-time so it's not perfect.
func fermatInverse(k, P *big.Int) *big.Int {
	two := big.NewInt(2)
	pMinus2 := new(big.Int).Sub(P, two)
	return new(big.Int).Exp(k, pMinus2, P)
}

// Sign signs an arbitrary length hash (which should be the result of hashing a
// larger message) using the private key, priv. It returns the signature as a